1. Field of the Invention
The present invention relates to methods for corrosion protection of steel workpieces, and more particularly to methods for depositing a cadmium-replacement or cadmium-alternative plating on steel workpieces.
2. Description of Related Art
Cadmium plating is used extensively for corrosion protection of steel workpieces, such as found in cartridge-activated devices and propellant-actuated (CAD/PAD) devices. Cadmium provides good corrosion protection, good lubricity, and may be applied as a thin coat so as not to conceal underlying surface formations and irregularities such as threads. However, the availability of cadmium for plating of steel is shrinking. Further, environmental protection regulations have restricted the use and handling of cadmium, which is considered to be toxic and a carcinogen.
Efforts have already been made to find a suitable cadmium replacement for coating steel parts. One potential replacement material is zinc-nickel alloy. Efforts to replace cadmium with zinc-nickel alloy have encountered certain problems. For example, conventional processes for plating zinc-nickel alloys have embrittled the steel substrate, causing premature failure of the steel. Zinc-Nickel plating has also been found to undergo dezincification corrosion.